Update .gitignore to allow !placement_engine.db

.gitignore

@@ -1,64 +1,65 @@
-# Python
-__pycache__/
-*.py[cod]
-*$py.class
-*.so
-.Python
-build/
-develop-eggs/
-dist/
-downloads/
-eggs/
-.eggs/
-lib/
-lib64/
-parts/
-sdist/
-var/
-wheels/
-*.egg-info/
-.installed.cfg
-*.egg
-.venv/
-venv/
-ENV/
-env/
-
-# Database
-*.db
-*.sqlite3
-*.db-journal
-*.db-wal
-*.db-shm
-
-# Frontend
-node_modules/
-dist/
-dist-ssr/
-*.local
-
-# Environment & Secrets
-.env
-.env.local
-*.pem
-*.key
-
-# Test & Lint
-.pytest_cache/
-.coverage
-htmlcov/
-.mypy_cache/
-.ruff_cache/
-.hypothesis/
-test-results/
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+.venv/
+venv/
+ENV/
+env/
+
+# Database
+*.db
+!placement_engine.db
+*.sqlite3
+*.db-journal
+*.db-wal
+*.db-shm
+
+# Frontend
+node_modules/
+dist/
+dist-ssr/
+*.local
+
+# Environment & Secrets
+.env
+.env.local
+*.pem
+*.key
+
+# Test & Lint
+.pytest_cache/
+.coverage
+htmlcov/
+.mypy_cache/
+.ruff_cache/
+.hypothesis/
+test-results/
 playwright-report/
-docs/pdf_pages/
-
-# IDE & OS
-.idea/
-.vscode/
-*.swp
-*.swo
-Thumbs.db
-Desktop.ini
-.DS_Store
+docs/pdf_pages/
+
+# IDE & OS
+.idea/
+.vscode/
+*.swp
+*.swo
+Thumbs.db
+Desktop.ini
+.DS_Store